Configure file
Introduction#
configure_file is a CMake function for copying a file to another location and modify its contents.
This function is very useful for generating configuration files with paths, custom variables, using a generic template.
Remarks#
Copy a file to another location and modify its contents.
configure_file(<input> <output>
[COPYONLY] [ESCAPE_QUOTES] [@ONLY]
[NEWLINE_STYLE [UNIX|DOS|WIN32|LF|CRLF] ])Copies a file to file
If the file is modified the build system will re-run CMake to re-configure the file and generate the build system again.
This command replaces any variables in the input file referenced as ${VAR} or @VAR@ with their values as determined by CMake. If a variable is not defined, it will be replaced with nothing. If COPYONLY is specified, then no variable expansion will take place. If ESCAPE_QUOTES is specified then any substituted quotes will be C-style escaped. The file will be configured with the current values of CMake variables. If @ONLY is specified, only variables of the form @VAR@ will be replaced and ${VAR} will be ignored. This is useful for configuring scripts that use ${VAR}.
Input file lines of the form “#cmakedefine VAR …” will be replaced with either “#define VAR …” or /* #undef VAR */ depending on whether VAR is set in CMake to any value not considered a false constant by the if() command. (Content of ”…”, if any, is processed as above.) Input file lines of the form “#cmakedefine01 VAR” will be replaced with either “#define VAR 1” or “#define VAR 0” similarly.
With NEWLINE_STYLE the line ending could be adjusted:
'UNIX' or 'LF' for \n, 'DOS', 'WIN32' or 'CRLF' for \r\n.COPYONLY must not be used with NEWLINE_STYLE.
Generate a c++ configure file with CMake
If we have a c++ project that uses a config.h configuration file with some custom paths or variables, we can generate it using CMake and a generic file config.h.in.
The config.h.in can be part of a git repository, while the generated file config.h will never be added, as it is generated from the current environment.
#CMakeLists.txt
CMAKE_MINIMUM_REQUIRED(VERSION 2.8.11)
SET(PROJ_NAME "myproject")
PROJECT(${PROJ_NAME})
SET(${PROJ_NAME}_DATA "" CACHE PATH "This directory contains all DATA and RESOURCES")
SET(THIRDPARTIES_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../thirdparties CACHE PATH "This directory contains thirdparties")
configure_file ("${CMAKE_CURRENT_SOURCE_DIR}/common/config.h.in"
"${CMAKE_CURRENT_SOURCE_DIR}/include/config.h" )If we have a config.h.in like this:
cmakedefine PATH_DATA "@myproject_DATA@"
cmakedefine THIRDPARTIES_PATH "@THIRDPARTIES_PATH@"The previous CMakeLists will generate a c++ header like this:
#define PATH_DATA "/home/user/projects/myproject/data"
#define THIRDPARTIES_PATH "/home/user/projects/myproject/thirdparties"Examble based on SDL2 control version
If you have a cmake module . You can create a folder called in to store all config files.
For example,you have a project called FOO, you can create a FOO_config.h.in file like:
//===================================================================================
// CMake configuration file, based on SDL 2 version header
// ===================================================================================
#pragma once
#include <string>
#include <sstream>
namespace yournamespace
{
/**
* \brief Information the version of FOO_PROJECT in use.
*
* Represents the library's version as three levels: major revision
* (increments with massive changes, additions, and enhancements),
* minor revision (increments with backwards-compatible changes to the
* major revision), and patchlevel (increments with fixes to the minor
* revision).
*
* \sa FOO_VERSION
* \sa FOO_GetVersion
*/
typedef struct FOO_version
{
int major; /**< major version */
int minor; /**< minor version */
int patch; /**< update version */
} FOO_version;
/* Printable format: "%d.%d.%d", MAJOR, MINOR, PATCHLEVEL
*/
#define FOO_MAJOR_VERSION 0
#define FOO_MINOR_VERSION 1
#define FOO_PATCHLEVEL 0
/**
* \brief Macro to determine FOO version program was compiled against.
*
* This macro fills in a FOO_version structure with the version of the
* library you compiled against. This is determined by what header the
* compiler uses. Note that if you dynamically linked the library, you might
* have a slightly newer or older version at runtime. That version can be
* determined with GUCpp_GetVersion(), which, unlike GUCpp_VERSION(),
* is not a macro.
*
* \param x A pointer to a FOO_version struct to initialize.
*
* \sa FOO_version
* \sa FOO_GetVersion
*/
#define FOO_VERSION(x) \
{ \
(x)->major = FOO_MAJOR_VERSION; \
(x)->minor = FOO_MINOR_VERSION; \
(x)->patch = FOO_PATCHLEVEL; \
}
/**
* This macro turns the version numbers into a numeric value:
* \verbatim
(1,2,3) -> (1203)
\endverbatim
*
* This assumes that there will never be more than 100 patchlevels.
*/
#define FOO_VERSIONNUM(X, Y, Z) \
((X)*1000 + (Y)*100 + (Z))
/**
* This is the version number macro for the current GUCpp version.
*/
#define FOO_COMPILEDVERSION \
FOO_VERSIONNUM(FOO_MAJOR_VERSION, FOO_MINOR_VERSION, FOO_PATCHLEVEL)
/**
* This macro will evaluate to true if compiled with FOO at least X.Y.Z.
*/
#define FOO_VERSION_ATLEAST(X, Y, Z) \
(FOO_COMPILEDVERSION >= FOO_VERSIONNUM(X, Y, Z))
}
// Paths
#cmakedefine FOO_PATH_MAIN "@FOO_PATH_MAIN@"This file will create a FOO_config.h in the install path, with a variable defined in c FOO_PATH_MAIN from cmake variable. To generate it you need to include in file in your CMakeLists.txt,like this (set paths and variables):
MESSAGE("Configuring FOO_config.h ...")
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/common/in/FOO_config.h.in"
"${FOO_PATH_INSTALL}/common/include/FOO_config.h" )That file will contain the data from template, and variable with your real path, for example:
// Paths
#define FOO_PATH_MAIN "/home/YOUR_USER/Respositories/git/foo_project"